Precision Measurements of Radiative Decay width and Transition Form Factor of 0,, and

PrimEx Experiments and the Prospects of Rare Decays at GlueXLiping GanUniversity of North Carolina Wilmington

Outline

Challenges in Physics

Precision tests of continuous symmetries of confinement QCD via the PrimEx experiments

Testing discrete symmetries and searching for new physics via the rare decays

Summary11Challenges in PhysicsConfinement QCD Lattice QCD Chiral perturbation theory

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QCD at different energiesNew physics beyond the Standard Model (SM) New sources of symmetry violation Dark matter Dark energy As far as I see, all a priori statements in physics have their origin in symmetry. By H. WeylContinuous symmetries of confinement QCD chiral limit: is the limit of vanishing quark masses mq 0. QCD Lagrangian with quark masses set to zero:

Large global symmetry group:

3 Fate of QCD symmetries

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Lightest pseudoscalar mesons Chiral SUL(3)XSUR(3) spontaneously broken Goldstone mesons 0, 8

Chiral anomalies Mass of 0 P ( P: 0, , )

Quark flavor SU(3) breaking The mixing of 0, and

The 0, and system provides a rich laboratory to study the symmetry structure of QCD at low energy.5 Primakoff Program at Jlab 6 & 12 GeV

Precision measurements of electromagnetic properties of 0, , via Primakoff effect.

Two-Photon Decay Widths: (0) @ 6 GeV() ()

Transition Form Factors at low Q2 (0.001-0.5 GeV2/c2):F(* 0), F(* ), F(* )

Input to Physics: precision tests of Chiral symmetry and anomalies determination of light quark mass ratio - mixing angleInput to Physics: 0, and electromagnetic interaction radii is the an approximate Goldstone boson?66(0) Experiments @ 6 GeV

0 decay proceeds primarily via the chiral anomaly in QCD. The chiral anomaly prediction is exact for massless quarks: Corrections to the chiral anomaly prediction:Calculations in NLO ChPT:(0) = 8.10eV 1.0% (J. Goity, et al. Phys. Rev. D66:076014, 2002)(0) = 8.06eV 1.0% (B. Ananthanarayan et al. JHEP 05:052, 2002)Calculations in NNLO SU(2) ChPT:(0) = 8.09eV 1.3% (K. Kampf et al. Phys. Rev. D79:076005, 2009)

Precision measurements of (0) at the percent level will provide a stringent test of a fundamental prediction of QCD. Calculations in QCD sum rule:(0) = 7.93eV 1.5% (B.L. Ioffe, et al. Phys. Lett. B647, p. 389, 2007) (0) is one of the few quantities in confinement region that QCD can calculate precisely to higher orders! 7k1k2

8Primakoff Method

,Challenge: Extract the Primakoff amplitude

12C target Primakoff Nucl. CoherentInterference Nucl. Incoh.

Requirement:Photon fluxBeam energy0 production Angular resolution

Features of Primakoff cross section:Peaked at very small forward angle:

Beam energy sensitive:

Coherent process

PrimEx-I (2004)

JLab Hall B high resolution, high intensity photon tagging facility New pair spectrometer for photon flux control at high beam intensities 1% accuracy has been achieved New high resolution hybrid multi-channel calorimeter (HyCal)

9Fit Differential Cross Sections to Extract (0) Theoretical angular distributions smeared with experimental resolutions are fit to the data on two nuclear targets:

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PrimEx-I ResultPRL 106, 162303 (2011)(0) = 7.820.14(stat)0.17(syst) eV2.8% total uncertainty11 Systematical uncertainty verification: Compton Cross Section Measurement

Data with radiative corrections

11Goal for PrimEx-II (2010)12

PrimEx-II projected 1.4%12

PrimEx-II Experimental Yield (preliminary)~8K Primakoff events12C

28Si~20K Primakoff events( E = 4.4-5.3 GeV)PrimakoffPrimakoff13 Outcomes from () Experiment @ 12 GeV

Extract - mixing angle: Determine Light quark mass ratio: H. Leutwyler Phys. Lett., B378, 313 (1996)Resolve long standing discrepancy between collider and Primakoff measurements:

(3) |A|2 Q-4

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~3.2% uncertainty1415 Challenges in the experiment

larger momentum transfer (coherency, form factors, FSI,) mass is a factor of 4 larger than 0 and has a smaller cross section larger overlap between Primakoff and hadronic processes;Compared to 0:

Cornell experiment (PRL, 1974): untagged bremsstrahlung beam, E=5.8, 9.0, 11.45 GeV targets: Be, Al, Cu, Ag, U Pb-glass calorimeterResult: ()=(0.3240.046) keV 14.2% total uncertainty

151616Advantages of the Proposed Light Targets Precision measurements require low A targets to control: contributions from nuclear processescoherency Hydrogen: no inelastic hadronic contribution no nuclear final state interactions proton form factor is well known better separation between Primakoff and nuclear processes new theoretical developments of Regge description of hadronic processes J.M. Laget, Phys. Rev. C72, (2005) A. Sibirtsev, et al. arXiv:1001.0646, (2010) 4He: higher Primakoff cross section: the most compact nucleus form factor well known new theoretical developments for FSI

S. Gevorkyan et al., Phys. Rev. C 80, (2009)

Hydrogen 4He targets 161717Measurement of () in Hall D at 12 GeVIncoherent tagged photon beam (~10.5-11.5 GeV) Pair spectrometer and a TAC detector for the photon flux control 30 cm liquid Hydrogen and 4He targets (~3.6% r.l.) Forward Calorimeter (FCAL) for decay photons CompCal and FCAL to measure well-known Compton scattering for control of overall systematic uncertainties.Solenoid detectors and forward tracking detectors (for background rejection)

CompCal FCAL

17Transition Form Factors F(*p) (at Low Q2)Direct measurement of slopes

Interaction radii:F*P(Q2)1-1/6PQ2

ChPT for large Nc predicts relation between the three slopes. Extraction of (p6) low-energy constant in the chiral Lagrangian

Input for light-by-light scattering for muon (g-2) calculation

Test of future lattice calculations

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Why is an unique probe for New physics ?Due to the symmetries in the strong and EM interactions, the decay width =1.3KeV is extremely narrow (relative to =149MeV)The lowest orders of decays are filtered out in the strong and EM interactions, enhancing the contributions from higher orders by a factor of ~100,000. decays is a unique probe to test SM and to search for new physics beyond SM: (1) test higher order PTh and future lattice QCD predictions; (2) new sources of fundamental symmetry violations; (3) light dark matter.

The most massive member in the octet of pseudoscalar Goldstone mesons (547.9 MeV/c2) Many open decay channels Sensitive to QCD symmetry breakings

Eigenstate of P, C, CP, and G: Study violations of discrete symmetries

The decays are flavor-conserving reactions which are effectively free of SM backgrounds for new physics search. 1919 Neutral Rare Decay Channels Mode

Branching Ratio(PDG)Physics Highlight0 2(2.70.5)104PTh @ (p6), Lattice QCD20